Circadian ethylene production in cotton

Light strongly influences plant processes and is instrumental inestablishing patterns in photosynthetic responses, enzymatic activity, andlevels of some plant hormones. At this time, it is unclear how the biosynthesisof the plant hormone ethylene is influenced by light in cotton cotyledonarytissue. To answer this question, the cotton (Gossypiumhirsutum L.) cultivar ‘DPL50’ was exposed to thefollowing light and/or dark treatments over a 72-h period: a12-h photoperiod, continuous light, or continuous dark. Ethylene,1-aminocyclopropane-1-carboxylic acid (ACC), andN-malonyl-1-aminocyclopropane-1-carboxylic acid (MACC) were assayed from wholeplant samples. Cotton plants exhibited a pattern of ethylene evolution thatappears to be controlled by a circadian clock. This circadian pattern wassuggested by the lack of change in ethylene evolution rate under continuouslight. The pattern of ethylene evolution was disrupted during a continuous darktreatment, indicating that light in some way is responsible for setting thecircadian clock for ethylene evolution and that light-sensing molecules such asphytochrome may be involved. Patterns of ACC and MACC concentration were notcircadian.